The purpose of the proposed experiments is to determine empirical relationships between auditory nerve single-fiber tuning (amplitude and phase) and otoacoustic emissions (OAE). The extent to which OAEs can be used to describe auditory processes, such as tuning, has recently been questioned (e.g., Siegel et al., 2005;Ruggero and Temchin, 2005, 2007). Much of the uncertainty reflects the wide inter- and intra-ear variability of single-fiber and OAE measures. Previous attempts to determine relationships were limited to using data acquired for other purposes. In particular, single-fiber measures were acquired from one group of ears while OAE measures were obtained from different ears with different stimuli. Here we propose what no one has yet done: to measure single-fiber tuning (amplitude and phase) and OAEs from the same ears, using the same stimuli, recorded closely in time. The results from these experiments will be to used to 1) determine how, or if, OAEs can be used as an ear-specific probe for cochlear tuning, 2) resolve the question about whether OAE propagation toward the ear canal is dominated by a slowly moving reverse traveling wave or by a fast moving compressional wave, and 3) provide the data needed to test theoretically driven models of OAE generation. Public Health Statement: The results of this work will describe the relationship between non-invasively recordable otoacoustic emissions and auditory processes that can only be measured with invasive surgical or psychoacoustic techniques that are difficult to do in humans. Our research will provide a better understanding of how otoacoustic emissions can be used as probes for normal auditory processes so that we can ultimately understand and ameliorate cochlear pathologies.